High performance semiconducting devices now require more innovative circuit design. Each increase in speed and power generally carries a cost of increased size such that additional innovations must be in order to minimize the size of semiconducting device packages.
Several methods have been employed to minimize the package size of semiconducting packages. One method includes encapsulating a plurality of dice or chips onto a tape substrate to form capsules and then folding the tape substrate to place the capsules one on top of another.
FIGS. 1-3 illustrate such a prior art semiconducting package 10. Semiconducting package 10 includes three capsules 21, 22, 23 that are encapsulated on a front side 14 of tape substrate 12. Each capsule 21, 22, 23 may have one or more dice encapsulated therein. The distance between each capsule 21, 22, 23 on tape substrate 12 will vary depending on the thickness and flexibility of tape substrate 12 as well as the size of the capsules 21, 22, 23. The distance between capsules 21 and 22 shown in FIG. 1 is equal to the distance between capsules 21 and 23. In other packages, the distances between capsules may vary depending on how the capsules are stacked together. As the number and arrangement of capsules changes, the distances between adjacent capsules changes accordingly.
The electronics circuits in capsules 21, 22, 23 communicate with each other through conductive paths formed in tape substrate 12. The thickness of capsules 21, 22, 23 is typically about 0.2 millimeter (mm) and the thickness of tape substrate 12 is typically about 0.1 mm. The distances between device units 21-23 is typically in the range 0.9-2.1 mm.
The dice may be encapsulated by any known procedure, such as molding and sealing. Other fabrication processes such as wire bonding, lead bonding, bump bonding, and die stacking are typically done to device units 21-23 prior to encapsulation. In addition, device units 21-23 are often subjected to additional processes such as ball attaching and/or marking after encapsulation. It should be noted that semiconducting device packages may include any number of device units formed on the front and/or back sides 14, 16 of tape substrate 12.
As shown in FIG. 2, the packaging process includes folding the tape substrate 12 to stack the capsules 21, 22, 23. An adhesive is manually or automatically dispensed between capsules 21, 22, 23 in the stack and cured to hold the package together. Each layer of adhesive increases the thickness, or “Z” height, of the package.
FIG. 3 shows capsule 21 in greater detail. Capsule 21 includes a die 24 that is mounted on the front side 14 of tape substrate 12 by encapsulating die 24 within an epoxy 25 or some other suitable material. Solder balls 15 in a ball grid array are mounted on the back side 16 of tape substrate 12 to form an electrical-mechanical connection between capsule 21 and other electrical devices. Capsule 21 is typically electrically connected to tape substrate 12 at its mating surface as well as via wire bonds 17.
Capsule 21 includes a flat upper surface 27 that mates with a similar flat surface on another capsule such as capsule 22 after tape substrate 12 has been folded. An adhesive is positioned between the flat mating surfaces of adjacent capsules 21, 22 to secure capsules 21, 22 together. The thickness of the adhesive detrimentally adds to the Z height of existing semiconducting packages. As shown in FIG. 2, capsule 23 is secured to capsules 21, 22 by folding tape substrate 12 to position capsule 23 against a back side of tape substrate 12 opposite to capsule 22.
One of the goals in semiconducting device packaging is to reduce the Z height of the packages. Therefore, it would be desirable to be able to adhere several stacked dice together into a package without adding significant Z height to the package. Any improvements in packaging semiconducting devices that include stacked dice would also not add significantly to the cost of fabricating such semiconducting devices.